High transconductance electron tube



Apnl 12, 1960 w. J. HELWIG HIGH TRANSCONDUCTANCE ELECTRON TUBE Filed April 4, 1958 3 Sheets-Sheet 1 I m I u IN VEN TOR. WILLIAM J. HE LWIE rrjvim'tf April 12, 1960 w. J. HELWlG HIGH TRANSCONDUCTANCE ELECTRON TUBE 3 Sheets-Sheet 2 Filed April 4. 1958 INVENTOR. VZI L LIAM J. HE LWIE 77% 45 1! ATTOA'A/E) HIGH TRANSCONDUCTAN CE ELECTRON TUBE William J. Helwig, Kearny, assignor to Radio Con poration of America, a corporation of Delaware Application April 4, 1958, Serial No. 726,366

Claims. (Cl. 313-268) The present invention relates to electron tubes and particularly to an improved electron tube having a mount or rugged construction which is adapted to contribute to the transconductance characteristic of a tube in which it is used.

The transconductanee characteristic of an electron tube is related to several factors. One of these factors is the physical spacing between a cathode and control grid utilized therein. It is known that a decrease in such spacing is accompanied by an increase in transconductance. However, if the spacing is reduced to a degree required for a relatively high transconductance characteristic, the spacing becomes so small that difiiculties in manufacture are encountered, and a severe burden is placed on electrode support elements. Such support elements must be suificiently rugged to restrain even relatively small magnitudes of relative movement of the electrodes to avoid contacts therebetween. The supports for the cathode and grid have a particular burden in this respect, since the spacing between these electrodes is more critical for high transconductance, than the spacing between other elements.

Another factor atfecting the transconductance of a tube is the reactance between elements thereof. It is to be noted that as the operating frequency is increased, both capacitive and inductive reactance assume a magnitude or appreciable concern.

Accordingly, it is an object of the invention to provide an improved high transconductance electron tube.

Other purposes of the invention in accordance with the foregoing object are:

To provide a novel cathode-grid subassembly in which a relatively close spacing between the cathode and grid is preserved by rugged support elements for these electrodes;

To provide a novel jigging method for assembling tube parts in critically spaced relation and fixing them in this relation; v

To provide relatively rugged electrode connectors adapted to constitute the sole supports for electrodes, thereby avoiding the need for mica spacers and minimizing stray capacities arising by virtue of such spacers;

To provide electrode connectors which in addition to being relatively rugged for supporting electrodes, are also relatively wide for reducing inductive reactance therein;

and a To provide relatively wide electrode connectors disposed in such fashion that an edge of one connector faces a flat side of another connector, for reducingv capacitive reactance therebetween. V

A feature of the invention relates to metallic plateliite supports for electrodes adapted to serve as connectors and directly fixed to lead-ins incorporated in a tube stem.

Another feature concerns the use of an insulated tube having ends fixed to the plate-like supports in engagements of relatively large area, for ruggedized restraint to relative movement of the plate-like supports and the electrodes supported thereby.

2,932,757 Patented Apr. 12, 1960 Further objects and features of the invention will become apparent as the description proceeds.

The accompanying drawing illustrates several embodiments of the invention by way of example. In the drawmg:

Fig. 1 is an exploded perspective view of the parts constituting an electrode mount according to the invention;

Fig. 2 shows a sectional elevation of tube parts assembled on a jig for forming a cathode subassembly;

Fig. 3 is a perspective view of a cathode subassembly resulting from the assembling operation depicted in Fig. 2;

Fig. 4 shows a sectional elevation of tube parts assembled on a jig for forming a grid subassembly;

Fig. 5 shows a perspective view, partly broken away, of a completed grid subassembly;

Fig. 6 is a sectional view in elevation of the cathode and grid subassemblies mounted on a jig for forming a cathode-grid subassembly;

Fig. 7 shows in perspective a complete cathode-grid Fig. 11 is a plan View of the stem forming part of the mount referred to;

Fig. 12 is a perspective view of a modified form of anode that may be used according to the invention;

Fig. 13 is an elevational view partly in section of a tube incorporating the anode shown in Fig. 12; and

Fig. 14 is a side elevational view of a further modification wherein an electrode cage of the type shown in Fig. 13, is mounted transversely of a tube stem.

It will be noted from the foregoing brief description of: the figures of the drawing, that three embodiments of the invention are illustrated. In two embodiments, which are shown in Figs. 1 to 11, and Fig. 14-, the several electrodes are mounted so that their several axes extend across a tube stem. In Figs. 12 and 13, the electrodes are mounted in substantially coaxial relation to the stem. in each of these embodiments, the cathode-grid subassemblies to be described are similar. However, the anode structures shown in Figs. 12 to 14 are difierent from the anode structure shown in Figs. 1 to 11, to allow the anode to accommodate itself to the requirements of each embodiment.

The embodiment illustrated in Figs. 1 to 11 comprises an electron tube mount having parts shown in exploded relation, in Fig. 1. These parts, when assembled, are ada ted to form an electron tube mount shown in Fig. l6. While the parts shown in Fig. 1 will be described in greater functional detail in connection with Figs. 2 to it), they may be stated, by way of tabulation, to comprise a stem 18, a first conducting plate 19 which may be made of nickel, a first ring 20 of brazing material, a cathode support 211 made for example of an alloy known as Kovar, a cathode 22 having a suitable emitting coating thereon, a second ring 23 of brazing material, a spacing and insulating cylinder or tube 24 which may be made of a ceramic material such as is known com mercially as Forsterite, a support ring 25, a second con ducting plate 26, a third ring 27 of brazing material, a cylinder grid 28, and an anode 29 made of two parts 3%, 31.

According to the invention, the parts referred to are assembled and mounted on the stem 18 (Fig. 9) in four stages for improved accuracy in spacing between electrodes thereof.

The fourstages referred to are depicted-in Figs. 2, 4,

6 and 9, and will now be described in more detail.

The first stage (Fig. 2) results in the assembly of a cathode subassembly shown in Fig. 3. In the assembling operation carried out at this stage, use is made of a jig 33 having a relatively large diameter cylindrical portion 34 defining shoulder 35, a smaller diameter cylindrical portion 36 defining a shoulder 37, and a still smaller diameter cylindrical portion 38. The parts to be assembled on this jig to form the cathode subassembly referred to are: the conducting plate 19, the brazing ring 20, the cathode support 21, and the cathode 22. In assembling these parts on the jig aforementioned, it is preferable first to position the tubular cathode support 21 over portion 36 of the jig and in seated relation on the shoulder 35. The diameter of jig portion 36 is such as to assure a snug fit with the cathode support 21. Thereafter, plate 19-, which may be rectangular, is extended over the cathode support 21, with the cathode support passing through an opening 39 in the plate, the opening having a diameter for snugly engaging the cathode support. The plate 19 thus becomes seated on shoulder 35. The ring 20 of brazing material comprising, for example, commercially available BT solder, is then threaded over the cathode support 21 until it comes to rest on the plate 19 and in contact relation with both the cathode support and the plate referred to.. Finally, the cathode 23 is telescoped over jig portion by which it is snugly received, and is seated on shoulder 37.

The jig 33 is machined to relatively close tolerances, so that the annular surface defined by shoulder 35 is in coaxial relation with respect to the common axis of jig portions 34, 36, 38. Therefore, in the position shown in Fig. 2, the cathode 22 is in accurate normal relation to the plate 19. The jig portion 36 is slightly shorter than the cathode support 22 to permit the cathode to telescope partly into the cathode support for a purpose to be described.

With the parts assembled as shown in Fig. 2, the jig is placed in a non-oxidizing atmosphere, such as hydrogen, and the jig portion 34-is heated by energy induced therein by a radio frequency induction coil 40 connected to a suitable source of electrical power, not shown. The heat produced in the jig portion 34 is conducted to jig portion 36 so that both the plate 19 and the cathode support 21 become heated to a suificiently high temperature to cause fusion of the ring 20 of brazing material, for fixing the plate 19 to the cathode support '21. Since the cathode support extends through the hole 39, the brazing material engages a portion of the support spaced from the adjacent end thereof, for improved ruggedness. A. welding electrode 41 connected to one terminal of a source of welding power, not shown, the jig 33 being connected to the other terminal, serves to join the adjacent overlapping end portions of the cathode support 21 and a cathode 22 in one continuous weld or a plurality of spot welds. To avoid inclusion of the jig in the brazing operation, it is preferably made of an alloy known in the trade as Nichrome and provided with an oxidized surface.

The foregoing operations of the first assembling stage complete the formation of the cathode subassembly shown in Fig. 3, which subassembly consists of plate 19, cathode support 21 and cathode 22 in fixed relation and with the cathode in accurate normal relation to the plane of plate 19. j

The second stage in the assembling of a tube mount according to the invention is illustrated in Fig. 4. A jig 42 includes a large diameter portion 43 defining a shoulder 44, on which the insulating cylinder 24 is adapted to rest. The jig also includes a smaller diameter portion 45 having a diameter for snugly engaging the inner wall of cylinder 24, and defining a shoulder 46 on which the grid 28 is adapted to be seated. A still smaller diameter portion 47 of the jig is snugly received by the grid 28. It will be noted that the jig portion 45 has a length equal to that of the cylinder 24. Therefore, the upper end surface of the cylinder 24 is flush with the shoulder 46 and is adapted to seat the support ring 25, which may be made of nickel. around the lower portion of grid 28. The upper surface of ring 25 provides an annular surface on which the plate 26 is seated. The plate 26 has an opening 4d of ,a diameter so that the walls defining the opening snugly engage the grid 23. Ring 27 of brazing material is then positioned to engage the grid 28 and the plate 26. After the parts have been assembled on the jig 42 as indicated, the jig is placed in a non-oxidizing atmosphere such as hydrogen and the portion 43 of the jig is heated by energy induced therein by a radio frequency induction coil 49 connected to a suitable power source, not shown. Heat produced in jig portion 43 is conducted through jig portion 45 to jig portion 47 and through grid 28 to the ring 27 of brazing material. When this ring softens in response to the heat thus conducted thereto, the ring material fiows inwardly through the openings in the grid 28 and serves to engage not only the plate 26, but also the grid 28 and metal ring 25, for fixing these parts together. Both end portions of the insulating cylinder 24 are provided with a metallic coating which may be made of sintered tungsten and iron particles, to which the brazing material referred to is adapted to adhere efiectively. Thus the aforementioned fusion of the brazing ring 27 causes brazing material to flow also in contact with the upper end surface of the cylinder 24 so that this cylinder also becomes joined to the elements previously mentioned. As in the case of the jig for assembling the cathode subassembly, the jig 42, currently under consideration, may be made of Nichrome and provided with an oxidizide surface.

The completed grid subassembly is shown in Fig. 5. Due to close tolerances in machining the jig aforementioned, and an accurate moulding or machining of the insulating cylinder 24, the grid 28 is in accurate coaxial relation with the insulating cylinder 24 and the common axis of the grid and cylinder is normal to the plane of plate 26. 7

The third stage in the assembling operation according to the invention, is illustrated in Fig. 6 and involves mounting and fixing the cathode and grid subassemblies previously described to form a cathode-grid subassembly shown in Fig. 7. Here again a jig 50 is utilized having a relatively large diameter portion 51, a smaller diameter portion 52, and a still smaller diameter portion 53. The jig portion 51 defines a shoulder 54 on which plate 19 of the cathode subassemblyis adapted to rest. The jig portion 52 has a diameter for snugly receiving the cathode support 21 and has a length for engaging the lower end of cathode 22 when the plate 19 is seated on shoulder 54. Jig portion 53 has a diameter for snugly receiving cathode 22. Also forming part of the jigging system is a cylinder 55 having a diameter for snugly receiving cathode 22 and a Wall thickness for snugly engaging the inner wall of grid 28. Therefore, when the grid subassembly is positioned on the jig, the lower end of the insulating cylinder 24 of the grid subassembly, rests on plate 19, and the jigging cylinder 55 rests on the upper end of cathode support 21. This results in a coaxial disposition of the insulating cylinder 24-, the oathode support 21, the cathode 22, and the grid 28. It results in a parallel disposition of the plates 19 and 26. For a purpose to be described it is preferable that the two subassemblies aforementioned be angularly oriented about the jig so that adjacent sides of the two plates are parallel, as shown in Fig. 7. Ring 23 of brazing material is heated by heat conducted to the plate 19 from the jig portion 51. This jig portion is heated by a radio frequency induction coil 56 connected to a suitable source The metal ring 25 is thus disposed of power, not shown. The heating step may be carried out in a suitable atmosphere such as hydrogen. The heat thus conducted to the brazing ring 23 causes it to fuse and become partly interposed between the plate 19 and the lower metalized end surface of the insulating ring 24. On completion of the assembling stage shown in Fig. 6, the cathode-grid subassembly shown in Fig. 7 is provided. In this assembly the cathode 22 and the grid 28 are ruggedly supported in coaxial relation by the plates 19 and 26 and the insulating cylinder 24. The relatively large area engagements between the cylinder 24 and the plates 19 and 26 contributes to the ruggedness of the support of the .two electrodes referred to.

The fourth stage in assembling an electron tube mount in accordance with the invention, involves utilization of a jig 57 shown in Fig. 8, and a jig 58 illustrated in Fig. 9. Jig 58 includes a relatively large diameter portion 59 which may serve as a handle for the jig, a smaller diameter portion 60 adapted to engage snugly the inner wall of cathode support 21, and a still smaller diameter portion 61 adapted to engage the inner wall of cathode 2.2 and the inner wall of a passageway 62, extending through jig 57. Jig 57 includes two slots 63, 64, adapted to receive anode wings 65, 66. The cavity 67 defined by jig 57 has a bottom 68 closing one end of the cavity, except for the passageway 62. The bottom 68 is more remote from the open end of cavity 67, than the bottoms 69, 7%) of the slots 63, 6 The resultant displacement of slot bottoms 69, 70 from the cavity bottom 68, in combination with a predetermined length of the cavity wall, assures a desired spacing between the anode and the plate 26 (Fig. 9), when the anode wings 65, 66 are urged against the slot bottoms referred to. While this spacing is relatively close, it will be noted that wings 65, 66 extend in planes normal to the plane of the plate 2-6, for reduced capacitive reactance. The open end of jig 57 serves as a stop against which the plate 2a is adapted to be seated as shown in Fig. 9. The cavity 67 has transverse dimensions for snugly receiving the tubular portion 71 of the anode. As a consequence, when the anode 29 is received in jig 57, and when jig 58 with the aforementioned cathode-grid subassembly assembled thereon has its portion 61 extended into passageway 62 in jig 57, the jigs may be said to be interlocked and the anode and cathode-grid subassemblies are properly positioned in relation to each other as shown in Fig. 9.

The lead-ins 72 extending through the stem disk 19, are preferably arrayed as shown in Fig. 11, to provide lead-ins 73, 74 disposed in one plane for fixing as by welding to spaced portions of the conducting plate 19 of the cathode subasserubly, to thereby provide a low inductance lead-in connection to the cathode 22. The array referred to also provides another group of leadins 75, 76, which are disposed in a plane parallel to the plane of lead-ins 73, 7d and spaced therefrom a distance to engage conducting plate 26 of the grid subassembly and to be fixed thereto, to thereby provide a low inductance energy path to the grid 28. Lead-in 77, in the array referred to, is spaced from the plane of lead-ins 75, 76 in a directionrernote from lead-ins 73,74, for fixedly engaging a wing 66 of the anode 29 to provide a low inductance lead-in connection for the anode.

I After the lead-ins referred to have been fixed to their associated electrodes aforementioned, jigs 5S and 57 are removed and a heater having legs 8% 81 is extended into the cathode 22. The heater legs may be fixed to lead-ins 78, '79 as shown in Figs. 10 and 11.

A bulb 18a may then be sealed to the periphery of stem 18, the stem 18 and the bulb 13a constituting an envelope for the tube, which may be suitably evacuated.

The resultant mount shown in Fig. 10 is characterized by rugged support of the electrodes thereof and by reduced reactance. The rugged support referred to permits very small spacings between the electrodes without danger of contact therebetween. The utilization of the relatively wide plates 19, 26 as connectors between electrodes and lead-ins, results in low inductance effects. The appreciable spacing between facing plates 19, 26, and the edge facing relation between the anode 29 and its wings 65, 66 with respect to the relatively close plate 226, results in reduced capacitive reactance. As a consequence a tube incorporating .the features just described, is characterized by relatively high transconductance during operation.

In the tube construction just described a rectangular shape of the conducting plates 19, 26 and the anode wing 66 is of advantage in that it renders it feasible for each plate 19, 26 to bridge the spacing between two lead-ins, to thereby more ruggedly mount the electrode subasseniblies on several lead-ins, for increased ruggedness of support. The rectangular shape of the anode wing 66 facilitates engagement between it and lead-in 77. if desired, the plates 19 and 26 and the anode wing 66 may be coextensive laterally from the electrode subassemblies so that the plates and the wing referred to may be caused to rest on the glass disk of stem 18 for further increasing the ruggedness of support of the electrode subassemblies on the stem, and for further reducing the length of the lead-ins for reduced reactance.

In the second embodiment of the invention shown in Figs. 12 and 13, the electrodes of a mount are positioned in coaxial relation with respect to a stem 82. This embodiment includes a cathode-grid subassembly similar to that previously described in relation to Figs. 1-10; This subassembly as previously noted, includes conducting plates 19, 25 and the insulating cylinder 24. it also includes a cathode support 21, a cathode 22 and a grid 25,

depicted in the first described embodiment, but not shown in detail in Figs. 12 and 13.

A more detailed consideration of the second embodiment in relation to Fig. 13 will reveal that a lead-in S3 is fixed to cathode connector plate 19, and a lead-in S4 is fixed to the grid connector plate 26. it is preferable that lead-ins 83 and so be disposed on opposite sides of the cathode-grid subassembly, for increased ruggedness of the mount. Anode 85 includes a tube portion 36 surrounding the grid 28 (not shown), and Wings 557, 88 having legs 89, 9d. The legs referred to extend along the insulating cylinder 24 and are fixed to a strap 91 fixedly embracing the cylinder aforementioned. In this manner the anode S5 is ruggedly supported on the cathode-grid subassernbly described before herein. A leadin 92 is fixed to one of the legs, 89, of the anode. The legs 89 and 99 are relatively wide and as a consequence, utilization of leg 89 as a connector between tubular anode portion 86 and lead-in 92 results in low inductance losses in the connector.

in the second embodiment of the invention'under consideration, it is feasible to mount the electrodes to form a self-supporting cage, prior to mountingfithe electrodes on the stem 82. This is not possible in connection with the embodiment shown in Figs. 1 to 11. The assembling operation to provide the electrode cage shown in Fig. 13, can be accompanied by suitable jigs, similar to those shown in Fig. 9, for supporting the anode and the cathode-grid subassembly in accurate coaxial relation during the step of fixing anode legs 89, 90 to the strap 91, this strap having previously been fixed around the insulating cylinder 24.

After the anode 85 and the cathode-grid subassembly has been assembled as indicated to provide a self-supporting cage, the cage is mounted on the stem 82.

For facilitating a mounting of the resultant electrode cage on the stem 82, the lead-ins 83, 84 and 92 of the stem may be provided with laterally extending hook portions at their free ends. referred to, to be conveniently fixed to the relatively wide connector elements comprising the plates 19, 26 and anode leg 89, as shown in Fig. 13.

This permits the lead-ins The array of the lead-ins in the stem disk in the secnd embodiment is not as critical as in the first de scribed embodiment due to the longer length of the leadins, as shown in Fig. 13. Such longer length allows appreciable latitude in orienting a particular lead-in with respect to a selected cage element. Lead-ins 93, 94 are connected to heater legs 80, 81 and do not require preforming since the heater legs are easily bendable to engage these lead-ins. A bulb 95 made of glass or other suitable material, sealed to stem 82 serves to complete an envelope, which is suitably evacuated.

The embodiment shown in Figs. l2 and 13 is characterized by ruggedness of support of the elements thereof, and reduced inductive and capacitive reactance for increased transconductance of a tube in which it is used.

In the third embodiment shown in Fig. 14, the electrode assembly depicted in Fig. 13, is mounted transversely of a stem 96. Stem 96 may be similar to stem 18 shown in Fig. 9. The electrode assembly comprises a self-supporting structure including the parts shown in Fig. 13, such as the anode 85 having legs 89, 90, fixed to a supporting band 91 embracing and fixed to the insulating tube 24. Wing 88 of the anode is fixed to lead-in 77. The conducting plates 19 and 26 are fixed to lead-ins 74, 76 respectively, and heater legs 80, 81 are fixed to lead-ins 78, 79 shown in Fig. 11. This construction results in a more rugged mount than in either of the two first described embodiments, in that the anode 85 is more securely supported by being fixed both to lead-in 77 and the insulating tube 24, and the lead-ins may be shorter. An envelope 97 sealed to stem 96 encloses the electrode assembly referred to, in a vacuum tight manner.

The first and third embodiments involving a transverse mounting of the electrode elements are of advantage in tubes wherein the electrode elements are small in relation to a stem. The second embodiment is of advantagewhen it is desired to mount the electrodes in coaxial relation with respect to a stem and when the electrodes are long in relation to the transverse extent of the stem. In each case however, the structure is such as to contribute to tube ruggedness and high transconductance.

What is claimed is:

1. An electrode subassembly for an electron tube comprising a stem having at least two lead-ins spaced thereacross, a first flat metallic plate having a tubular cathode supported thereon in normal relation to the plane of said plate, a second fiat metallic plate having a tubular grid supported thereon in normal relation to the plane of said second plate, and an insulating member having parallel ends fixed to facing surfaces of said plates for disposing and preserving said cathode and grid in coaxial relation, said insulating member having a length for disposing said plates in engagement with said leadins, said plates being fixed to said lead-ins for preserving a desired orientation of said subassembly with respect to said stem.

2. An electron tube having a mount comprising a stem having at least three lead-ins spaced thereacross, a cathode subassembly including a first flat metallic plate fixed to one of said lead-ins, a tubular cathode supported on saidplate in normal relation thereto, a grid subassembly including a second fiat metallic plate fixed to the next adjacent one of said lead-ins and disposed in spaced parallel relation to said first plate, a tubular grid supported on said second plate and in concentric relation with respect to said cathode, an insulating member having parallel fiat end surfaces .fixed to facing surfaces of said plates for preserving said concentric relation of the cathode and grid, and a tubular anode in concentric relattion to said cathode and grid, said anode including a planar portion normal to said plates and fixed to the third of said lead-ins, for preserving said concentric relation of said anode with respect to said cathode and grid v 3. A grid subassembly for an electron tube comprising a metallic fiat plate having an opening therethrough, a tubular grid extending through said opening, a metallic ring fixed to one face of said plate and adjacent to said opening, one end portion of said grid being fixed to the walls defining said opening and to said ring, whereby said grid is ruggedly mounted on said plate, and a tubular insulating member fixed to said ring in coaxialrelation with respect to said grid, for spacing said grid from an adjacent electrode subassembly.

4. An electron tube having an electrode assembly comprising a tubular insulating member having parallel end surfaces normal to the axis of said member, two flat metallic plates fixed to said end surfaces, a tubular cathode supported on one of said plates and extending beyond the other of said plates in normal relation thereto, a tubular grid supported on said other of said plates and extending therefrom in concentric relation with respect to said cathode, an envelope enclosing said assembly, and lead-ins extending through said envelope and connected to said plates.

5. A high transconductance electron tube comprising a tubular cathode, a tubular grid, a tubular anode, platelike electrical connectors supporting said cathode and grid, whereby said connectors provide relatively low inductance paths to said cathode and grid, said connectors being disposed in parallel planes for increased ruggedness of the support provided thereby, said planes being spaced sufficiently to preserve said connectors from objectionable capacitance effects, and a flat connector supporting said anode, said last named connector being disposed in a plane normal to the plane of said plate-like connectors, whereby capacitance between said flat connector and said plate-like connectors and inductance in said flat connector, are reduced.

6. An electron tube comprising a stem including a flat disk made of insulating material, a plurality of leadins disposed in a predetermined array, said array comprising a first group of two spaced lead-ins, a second group of lead-ins spaced in a plane parallel to and spaced from the plane of said first group, and a third group of lead-ins including at least one lead-in spaced from the plane of said second group of lead-ins in a direction remote from said first group, a cathode, a fiat connector plate supporting and connected to said cathode and disposed in normal relation to said disk, said connector plate being fixed to said first group of lead-ins, a grid surrounding said cathode, a flat connector plate fixed to'said grid for supporting the same and disposed in parallel relation to said first named connector plate, said last named connector plate being connected to said second group of lead-ins, and a flat connector wing fixed to said anode, said connector wing being fixed to said third group of lead-ins for supporting said anode, said flat connector plates and said connector Wing being disposed in planes normal to said disk, said connector wing being disposed in a plane normal to said connector plates, whereby said electrodes are ruggedly mounted on said stem and said connector plates and wing are characterized by reduced reactance.

7. An electron tube comprising a stem having 1ead-ins extending therethrough, an electrode subassembly comprising an elongated insulating cylinder, a cathode, a first means supporting said cathode on one end of said cylinder, a grid, a second means supporting said grid on the other end of said cylinder, "an anode, and a third means extending from said anode and supporting said anode on a portion of said cylinder intermediate the ends of said cylinder, said first, second and third supporting means being connected to diiferent ones of said lead-ins.

8. An electron tube according to claim 7 and wherein said first, second and third supporting means comprise fiat planar structures for reduced inductance therein and for increased ruggedness of support provided thereby,

9. An electron tube according to claim 7, and wherein said stem is fiat and said cylinder, cathode, grid and anode are coaxial and mounted transversely of said stem.

10. An electrode assembly comprising two spaced parallel conducting plates, an elongated insulating cylinder having its ends fixed to said plates, a cathode extending from one end of said cylinder and fixed to one of said plates adjacent to the other end of said cylinder, a tubular grid extending from said one end of the cylinder and surrounding said cathode, said grid being mounted on the other of said plates, support means fixed to and extending laterally from said insulating cylinder,

and an anode surrounding said grid and having two oppositely disposed legs fixed to said support means.

References Cited in the file of this patent UNITED STATES PATENTS 2,062,892 Laico Dec. 1, 1936 $582,684 Drieschman Jan. 15, 1952 2,708,249 Pryslak May 10, 1955 2,719,244 Dailey Sept. 27, 1955 2,724,069 Young Nov. 15, 1955 2,753,615 Claude July 10, 1956 2,790,228 Koda Apr. 30, 19-57 

